Inductive head and magnetic disk apparatus

ABSTRACT

In a convention inductive head, since a large magnetic field is leaked from the end of the magnetic pole end of an upper magnetic core, at recording the recording magnetic field is applied to a recording media in a region larger than a desired track width, thereby damaging the adjacent information.  
     In an inductive head according to the present invention, in order to efficiently carry a magnetic flux to a magnetic pole tip layer, the top surface of the rear end of the magnetic pole tip layer is etched away so as to connect the rear end of the magnetic pole tip layer to the front end of an upper magnetic core having a width larger than that of the rear end of the magnetic pole tip layer. It is possible to realize a recording head having a large recording magnetic field. In addition, the front end of the upper magnetic core is recessed from an air bearing surface by 0.2 to 3.0 μm so as to reduce the magnetic field leaked from the end of the upper magnetic core.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an inductive head for use inmagnetic recording.

[0003] 2. Description of the Related Art

[0004] With increasing recording density of magnetic disk apparatuses,magnetic recording media enhance the coercivity, and the track width ofinductive heads for use in recording is made smaller. In addition, asthe coercivity of the magnetic recording media is made higher, thethickness of the inductive heads is increased in order to provide amagnetic flux enough for recording. At present, the thickness of thefront end of an upper magnetic core of the inductive heads is increasedas compared with the track width, thereby making it more difficult tomanufacture them.

[0005] In order to solve the problems, Japanese Unexamined PatentPublication No. Hei 7(95)-296328 describes the structure of an inductivehead having a trench with a smaller width than the width of the magneticpole end of the upper magnetic core of the inductive head, and the widthof the trench is defining a track width.

[0006] As described above, in the inductive head described in JapaneseUn-examined Patent Publication No. Hei 7(95)-296328, the width of themagnetic pole end of the upper magnetic core is larger than the magneticpole tip layer defining the track width. This structure can maintain thelarge magnetic flux on the front end of the upper magnetic core, so asto manufacture a magnetic pole tip layer having a small thickness and atrack width with high precision. However, a large magnetic field isleaked not only from the magnetic gap portion but also from the frontend portion of the upper magnetic core. At recording, the recordingmagnetic field is applied to the recording media in a region wider thana track width desired, thereby damaging adjacent information.

[0007] As one of means of solving the problem, in order to reduce themagnetic field leaked from the magnetic pole end portion of the uppermagnetic core, the upper magnetic core is constructed such that themagnetic pole end surface thereof is recessed from the air bearingsurface. However, in this case, as the magnetic field leaked is reduced,the recording magnetic field is small.

SUMMARY OF THE INVENTION

[0008] In order to realize a small track width, an inductive headaccording to the present invention forms a magnetic pole tip layerhaving a substantially track width at least near the air bearing surfacebetween an upper magnetic core and a lower magnetic core.

[0009] In order to efficiently carry the magnetic flux to the magneticpole tip layer, the top surface of the rear end of the magnetic pole tiplayer is milled, and then the rear end of the magnetic pole tip layer isconnected to the front end of the upper magnetic core having a widthlarger than that of the rear end of the magnetic pole tip layer, so asto realize a recording head having a large recording magnetic field.

[0010] When the front end of the upper magnetic core is exposed from theair bearing surface of the magnetic head, the magnetic field leaked fromthe both side of front end of the upper magnetic core can damageinformation of the adjacent track. In order to avoid this, in therecording head of the present invention, the front end of the uppermagnetic core is desirably recessed from the air bearing surface by 0.2to 3.0 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is an embodiment of an inductive head according to thepresent invention;

[0012]FIG. 2 is a contour line diagram of the in-plane components of themagnetic field intensity of the inductive heads according to the presentinvention and the comparative examples;

[0013]FIG. 3 is a diagram showing a method of manufacturing theinductive head according to the present invention;

[0014]FIG. 4 is a cross-sectional view of another embodiment of theinductive head according to the present invention;

[0015]FIG. 5 is a cross-sectional view of a further embodiment of theinductive head according to the present invention;

[0016]FIG. 6 is a cross-sectional view of a still another embodiment ofthe inductive head according to the present invention; and

[0017]FIG. 7 is a diagram showing a magnetic disk apparatus using theinductive head according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Embodiments of the present invention will be described based onthe examples with reference to the drawings. FIG. 1 is a model diagramof the inductive head according to the present invention, in which FIG.1(a) is a cross-sectional view of the inductive head according to thepresent invention, and FIG. 1(b) is a top view viewed from the topsurface parallel to x direction shown in FIG. 1(a). As shown in FIG.1(a), the inductive head of the present invention comprises a lowermagnetic core 1 on a substrate, an upper magnetic core 2, and coils 3disposed around between the lower magnetic core and the upper magneticcore, the lower magnetic core 1 and the upper magnetic core 2 beingconnected by a back contact portion 4 in the rear end, and beingconnected through a magnetic pole tip layer 11 in the front end. Themagnetic pole tip layer 11 comprises a layer made by laminating a lowerside layer of the magnetic pole tip layer 111, a magnetic gap layer 10,and an upper side layer of the magnetic pole tip layer 112. The distancefrom the lower magnetic core 1 to the top surface of the magnetic poletip layer 11 of the rear end is smaller than that of the front end, andat least the rear end of the magnetic pole tip layer 11 is connected tothe front end of the upper magnetic core 2. The width of the front endof the upper magnetic core 2 is desirably larger than that of the rearend of the magnetic pole tip layer 11. Thus, the magnetic flux iseffectively flowed to the magnetic pole tip layer so as to provide aninductive head giving a high recording magnetic field.

[0019] FIGS. 2(c) and 2(d) show examples of the distribution of therecording magnetic fields of the inductive head of the presentinvention. For comparison, FIGS. 2(a) and 2(b) show examples of thedistribution of the recording magnetic fields of a conventionalinductive head. In either case, the thickness of the lower side layer ofthe magnetic pole tip layer is 0.5 μm, the thickness of the gap layer is0.2 μm, and the thickness of the upper side layer of the magnetic poleend layer is 2.0 μm. The saturation magnetic flux density Bs is 1.9T andthe specific permeability μ of the lower side layer and the upper sidelayer of the magnetic pole tip layer is 1500 of Co—Ni—Fe. The writefield distributions Hxz in the medium plane are calculated using athree-dimensional magnetic field simulator by Maxwell's equations inintegral form. In the magnetic pole tip layer, the width from the frontend to 0.5 μm is 0.34 μm, and then the shape is extended at a 20° angleto 3.0 μm. A difference between the length of the magnetic pole tiplayer and an amount recession of the front end of the upper magneticcore from the air bearing surface is a contact length of the magneticpole tip layer with the upper magnetic core. In either case, when thecontact length of the magnetic pole tip layer with the upper magneticcore is up to 5.0 μm, the longer the contact length, the larger themagnetic field becomes. In addition, as an amount of recession of thefront end of the upper magnetic core from the air bearing surface isincreased, the maximum magnetic field and the magnetic field leaked fromthe end of the upper magnetic core are reduced. The maximum magneticfield is reduced abruptly when an amount of recession of the front endof the upper magnetic core exceeds 3.0 μm, and the magnetic field leakedfrom the end of the upper magnetic core is almost constant when anamount of recession is not less than 0.2 μm. Thus, desirably, an amountof recession of the front end of the upper magnetic core is 0.2 to 3.0μm, and the length of the magnetic pole end layer is 2.0 to 7.0 μm.

[0020] As in this embodiment, when the magnetic pole tip layer has athree-layer structure of magnetic layer/non-magnetic layer/magneticlayer, and the three layers have the same shape viewed from the top, theangle of extension is 5 to 45°, so as to increase the recording magneticfield.

[0021] In the upper magnetic core, a width from the air bearing surfaceto 0.5 μm is 1.34 μm, and then the shape is extended at the angle ofextension of 40° to the core width of 30 μm. The lower magnetic core hasa thickness of 2.5 μm, and the upper magnetic core has a thickness of3.0 μm. The lower magnetic core and the upper magnetic core have Bs=1.6Tof 45Ni-55Fe, and μ=1600. The magnetomotive force is 0.36 At, andrecording magnetic field distribution in the medium plane in theposition 25 nm away from the air bearing surface is calculated using athree-dimensional magnetic field simulator by Maxwell's equations inintegral form. The calculated results are shown in contour line diagramsfor each about 40 kA/m (5000e). The sectional shapes of the front endsof the models are shown above the contour line diagrams. In the diagram,the vertical direction indicates a down track direction, the horizontaldirection indicates a track width direction, and the numerals are in μm.

[0022] In FIG. 2(a) as one example for comparison, the front end of themagnetic pole tip layer has the same thickness as that of the rear endthereof, and the front end of the upper magnetic core is exposed to theair bearing surface. The maximum magnetic field is 633 kA/m (7.97 kOe),and the magnetic field leaked from the both side of the front end of theupper magnetic core is large and 252 kA/m (3.18 kOe), so thatinformation of the adjacent track can be damaged.

[0023] In FIG. 2(b) as another example for comparison, the front end ofthe magnetic pole tip layer has the same thickness as that of the rearend thereof, and the front end of the upper magnetic core is recessedfrom the air bearing surface by 1.0 μm. The magnetic field leaked fromthe both side of the front end of the upper magnetic core is reduced tonot more than 79 kA/m (1000 Oe), and the maximum magnetic field isreduced to 625 kA/m (7.88 kOe).

[0024]FIG. 2(c) shows the inductive head according to the presentinvention wherein the front end of the upper magnetic core is exposed tothe air bearing surface. The maximum magnetic field is 647 kA/m (8.15kOe), and the magnetic field leaked from the both side of the front endof the upper magnetic core is 216 kA/m (2.72 kOe). As compared with FIG.2(a) as one example of the conventional inductive head, it is found thatthe maximum magnetic field is increased, and the magnetic field leakedfrom the upper magnetic core is reduced.

[0025]FIG. 2(d) shows the inductive head according to the presentinvention wherein the front end of the upper magnetic core is recessedfrom the air bearing surface by 1.0 μm. The magnetic field leaked fromthe both side of the front end of the upper magnetic core is reduced tonot more than 79 kA/m (1000 Oe), and the maximum magnetic field is 642kA/m (8.09 kOe). As compared with FIG. 2(b) as another example of theconventional inductive head, it is found that the maximum magnetic fieldis large. With respect to the shape of FIG. 2(d), when the lower andupper magnetic pole end layers have Bs=2.3T of 70Fe-30Co, and μ=100, themaximum magnetic field is increased to 717 kA/m (9.03 kOe). When thetrack width is 0.6 μm, it is increased to 788 kA/m (9.93 kOe). Thethickness of the magnetic gap layer and the shape of the magnetic poletip layer are optimized, so that it is expected that the maximummagnetic field is increased by about 79 kA/m (1.0 kOe) or furthermore.

[0026] In the inductive head of the present invention, a recording headhaving a small track width of 0.3 to 0.6 μm permits recording onto amedia having a coercivity of 317 to 476 kA/m (4.0 to 6.0 kOe) at a highS/N and recording density.

[0027]FIG. 3 shows one example of a method of manufacturing theinductive head according to the present invention.

[0028] The lower magnetic core 1 is formed on a substrate 6, and then aframe mask for forming the magnetic pole tip layer is formed, so as todefine the lower magnetic pole tip layer 111, the magnetic gap layer 10,and the upper magnetic pole tip layer 112 by a plating method.Thereafter, the unnecessary portion of the plating layer and the framemask are removed (FIG. 3(a)). When a magnetoresistive head, a spin valvehead, or a giant magnetoresistive head is used as the reproducing head,the lower magnetic core and the upper shield may be used together, or anon-magnetic layer may be interposed between the layers to be separated.

[0029] Coils of the first layer are formed, and then an insulating layersuch as Al2O3, SiO2, or resist is formed. After flattening treatment bya chemical mechanical polishing method, the rear portion of the uppermagnetic pole tip layer 112 is etched away using ion milling, reactiveion etching (R.I.E.), or wet etching (FIG. 3(c)).

[0030] In this case, the rear portion of the upper magnetic pole tiplayer may be etched away without flattening treatment (FIG. 3(c′)).Flattening treatment makes the process complicate, but a desired shapecan be easily given. The magnetic pole tip layer 11 may be formed beforeforming the coils.

[0031] Subsequently, coils of the second layer and so on are formed, athrough hole for the back contact is formed, the upper magnetic core 2is formed, and finally the protective layer is formed (FIG. 3(d)). Theback contact portion may employ the plating layer at forming themagnetic pole tip layer (FIG. 3(d′)), or may be formed with a newmagnetic layer.

[0032]FIG. 4 shows a cross-sectional view of the inductive head ofanother embodiment of the present invention. As shown in FIG. 1, formingthe magnetic pole tip layer 11 on the flat lower magnetic core 1 makesit easy to process a small track width. A non-magnetic layer isinterposed between the rear portion of the magnetic pole tip layer 11and the lower magnetic core 1 so as to give a higher recording magneticfield. The same effect can be given, when the top portion of themagnetic pole tip layer is subjected to flattening treatment, as shownin FIG. 4(a) or it is not subjected to flattening treatment, as shown inFIG. 4(b).

[0033]FIG. 5 shows a cross-sectional view of a further embodiment of theinductive head of the present invention. In FIG. 5, the magnetic gaplayer 10 is formed at least near the gap on the lower magnetic core 1, anon-magnetic layer separating the rear portion of the magnetic pole tiplayer 11 from the magnetic gap layer 10 is formed, so as to define themagnetic pole tip layer 11. Subsequently, using a mask including themagnetic pole tip layer 11, the magnetic gap layer 10 in a region notcovered with the mask at least near the air bearing surface and the topregion of the lower magnetic core are etched away by ion milling orR.I.E, so as to form the lower magnetic core 1 and the magnetic pole tiplayer 11 having a desired track width. As in this embodiment, themagnetic pole tip layer 11 is formed on the magnetic gap layer 10 andthe non-magnetic step layer. As the angle of extension of the magneticpole tip layer is increased, or the position of extension is close tothe air bearing surface, the magnetic field is higher. However, as theangle of extension of the magnetic pole tip layer 11 is increased, orthe position of extension is close to the lifting surface, it isdifficult to process the top surface of the lower magnetic core near thelifting surface into the shape having a desired track width.

[0034] In the present invention, the magnetic pole tip layer 11 having asmall angle of extension is formed, and then the magnetic gap layer andthe top portion of the lower magnetic core are processed into a desiredshape. Thereafter, the rear portion of the magnetic pole tip layer isetched to be connected to the upper magnetic core 2 having a widthlarger than the magnetic pole tip layer. Thus, it is possible to providean inductive head having high accuracy for the track width process andan intense magnetic field. The same effect can be given, when the topportion of the magnetic pole tip layer is subjected to flatteningtreatment, as shown in FIG. 5(a) or it is not subjected to flatteningtreatment, as shown in FIG. 5(b).

[0035] With respect to the shape of FIG. 5(a), the three dimensionalmagnetic field simulator under the following conditions is used tocalculate the magnetic field. The lower magnetic layer comprises twolayers made by laminating Co—Ni—Fe(1.9T) of 0.5 μm on 40 to 60Ni-60 to40Fe(1.6T) of 2.5 μm. The thickness of the gap layer is 0.2 μm, thethickness of the magnetic pole tip layer is 2.0 μm, and the saturationmagnetic flux density is 1.9T of Co—Ni—Fe. In the magnetic pole tiplayer, the width from the front end to 0.5 μm is 0.34 μm, and then theshape is extended at a 20° angle to 3.0 μm. The front end of the lowermagnetic core has a structure such that the region not covered with themagnetic pole tip layer or the non-magnetic step layer is etched by 0.5μm. In the upper magnetic core, the width from the flying surface to 0.5μm is 1.34 μm, and then the shape is extended at the angle of extensionof 40° to the core width of 30 μm. The thickness of the upper magneticcore is 3.0 μm, and the saturation magnetic flux density is 1.6T. Themagnetomotive force is 0.36 At. The maximum magnetic field is 647 kA/m(8.15 kOe), so as to give a recording magnetic field having an intensityslightly higher than that of the shape of FIG. 2(d). The portion ofCo—Ni—Fe is changed to Fe—Co (2.3T) so as to give a maximum magneticfield of 722 kA/m (9.10 kOe).

[0036]FIG. 6 shows a cross-sectional view of a still another embodimentof the inductive head of the present invention. In the embodiment ofFIG. 6, the coils 3 are formed on the lower magnetic core 1, and thenthe lower side layer of the magnetic pole tip layer 111 is formed atleast near the gap on the lower magnetic core 1. After flatteningtreatment, the magnetic gap layer 10 and the upper side layer of themagnetic pole tip layer 112 are formed. Subsequently, using a maskincluding the upper side layer of the magnetic pole tip layer, themagnetic gap layer 10 in a region not covered with the mask at leastnear the lifting surface and the top region of the lower side layer ofthe magnetic pole tip layer 111 are etched away by ion milling or R.I.E,so as to form the magnetic pole tip layer 11 having a desired trackwidth. Then, after forming the coils 3, the rear end of the upper sidelayer of the magnetic pole tip layer 112 is etched away by ion millingor R.I.E. Finally, the upper magnetic core 2 is formed. The same effectcan be given, when the top portion of the magnetic pole tip layer issubjected to flattening treatment, as shown in FIG. 6(a) or it is notsubjected to flattening treatment, as shown in FIG. 6(b).

[0037]FIG. 7 is a diagram showing a magnetic disk apparatus of oneembodiment using the inductive head according to the present invention.There is shown an outline such that the inductive head according to thepresent invention is applied to the magnetic disk apparatus as amagnetic recording apparatus. The inductive head of the presentinvention can be mounted on a magnetic recording apparatus such as amagnetic tape apparatus.

[0038] The magnetic disk apparatus illustrated comprises a magnetic disk1110 as a magnetic recording media formed on the disk for recording datain a recording region called a concentric track, a magnetic head 1118according to the present invention comprising a magnetic transducer forreading and writing the data, actuator means for supporting the magnetichead 1118 to move it to a predetermined position on the magnetic disk1110, and control means for controlling transmission and receive of databy read and written by the magnetic head 1118 and movement of theactuator means.

[0039] A plurality of magnetic disk apparatuses are connected to form adisk array apparatus having a large storage capacity.

[0040] Embodiments of the present invention can provide an inductivehead which can prevent the adjacent information from being damaged, havea small track width, and provide an intense magnetic field.

What is claimed is:
 1. An inductive head comprising a lower magneticcore formed on a substrate, a magnetic pole tip layer formed on thelower magnetic core, an upper magnetic core coupled in its front end tothe magnetic pole tip layer, coupled in its rear end to the lowermagnetic core, having a width of the front end smaller than that of therear end, and having at least partially a shape gradually reducing thewidth from the rear end to the front end, coils disposed around betweenthe upper magnetic core and the lower magnetic core, and an insulatinglayer formed between the coils and the upper magnetic core or the lowermagnetic core, wherein the distance between the top surface of themagnetic pole tip layer and the lower magnetic core in a rear end regionaway from an air bearing surface in a region connecting the magneticpole tip layer to said upper magnetic core is shorter than the distancebetween the top surface of said magnetic pole tip layer in the airbearing surface and said lower magnetic core.
 2. The inductive headaccording to claim 1, comprising a magnetic gap layer formed at leastnear the air bearing surface on said lower magnetic core, a non-magneticlayer for maintaining a thickness increased with moving away from theair bearing surface, in a region such that the magnetic gap layer ismoved away from the air bearing surface, or in a region such that themagnetic gap layer is moved away from the air bearing surface and in aregion such that the lower core is moved away from the air bearingsurface, and said magnetic pole tip layer formed on the magnetic gaplayer and the non-magnetic layer.
 3. An inductive head comprising alower magnetic core formed on a substrate, a magnetic pole tip layerformed on the lower magnetic core, an upper magnetic core coupled in itsfront end to the magnetic pole end layer, coupled in its rear end to thelower magnetic core, having a width of the front end smaller than thatof the rear end, and having at least partially a shape graduallyreducing the width from the rear end to the front end, coils disposedaround between the upper magnetic core and the lower magnetic core, andan insulating layer formed between the coils and the upper magnetic coreor the lower magnetic core, wherein the distance between the top surfaceof the upper magnetic core and the lower magnetic core in a rear endregion away from a air bearing surface in a region connecting themagnetic pole tip layer to said upper magnetic core is shorter than thedistance between the top surface of said magnetic pole tip layer in theair bearing surface and said lower magnetic core.
 4. The inductive headaccording to claim 3, comprising a magnetic gap layer formed at leastnear the air bearing surface on said lower magnetic core, a non-magneticlayer formed in a region such that at least the magnetic gap layer ismoved away from the air bearing surface and having a portion formaintaining a thickness increased with moving away from the air bearingsurface, and said magnetic pole tip layer formed on the magnetic gaplayer and the non-magnetic layer.
 5. The inductive head according toclaim 2, wherein said magnetic pole tip layer is formed on the lowermagnetic core near the air bearing surface, and is formed on thenon-magnetic layer formed on the lower magnetic core in the region awayfrom the air bearing surface.
 6. The inductive head according to claim4, wherein said magnetic pole tip layer is formed on the lower magneticcore near the air bearing surface, and is formed on the non-magneticlayer formed on the lower magnetic core in the region away from the airbearing surface.
 7. The inductive head according to claim 1, whereinsaid magnetic pole tip layer comprises three layers of magneticlayer/non-magnetic layer/magnetic layer.
 8. The inductive head accordingto claim 3, wherein said magnetic pole tip layer comprises three layersof magnetic layer/non-magnetic layer/magnetic layer.
 9. The inductivehead according to claim 5, wherein said magnetic pole tip layercomprises three layers of magnetic layer/non-magnetic layer/magneticlayer.
 10. The inductive head according to claim 6, wherein saidmagnetic pole tip layer comprises three layers of magneticlayer/non-magnetic layer/magnetic layer.
 11. The inductive headaccording to claim 1, wherein the front end of said upper magnetic coreis recessed from the air bearing surface by 0.2 to 3.0 μm.
 12. Theinductive head according to claim 3, wherein the front end of said uppermagnetic core is recessed from the air bearing lifting surface by 0.2 to3.0 μm.
 13. The inductive head according to claim 1, wherein thesaturation magnetic flux density of the magnetic pole tip layer ishigher than that of any one of at least the upper magnetic core and thelower magnetic core.
 14. The inductive head according to claim 3,wherein the saturation magnetic flux density of the magnetic pole tiplayer is higher than that of any one of at least the upper magnetic-coreand the lower magnetic core.
 15. A magnetic disk apparatus comprising amagnetic recording media, a motor driving the same, a magnetic head forread and write onto the magnetic recording media, and a mechanism forpositioning the magnetic head, wherein at least one inductive headaccording to claim 1 is mounted as the write head, a width of themagnetic pole tip layer of said head in the air bearing flying surfaceis not more than 0.5 μm, the saturation magnetic flux density of themagnetic layer consisting of the magnetic pole layer is not less than1.6T, and the coercivity of the magnetic recording media is 317 to 634kA/m (4.0 to 8.0 kOe).
 16. A magnetic disk array apparatus comprising aplurality of the magnetic disk apparatuses connected, wherein at leastone inductive head according to claim 1 is mounted as the write head, awidth of the magnetic pole tip layer of said head in the air bearingsurface is not more than 0.5 μm, the saturation magnetic flux density ofthe magnetic layer consisting of the magnetic pole layer is not lessthan 1.6T, and the coercivity of the magnetic recording media is 317 to634 kA/m (4.0 to 8.0 kOe).